Heretofore, others have suggested increasing the downward velocity of threshed material and the velocity of the transverse air stream used to effect aerodynamic separation of the chaff from the grain. A technical paper "Aerodynamic Separation in a Combine Shoe" by D. W. Rumble and J. H. A. Lee prepared for presentation at the Dec. 10-13, 1968 meeting of the American Society of Agricultural Engineers at Chicago, Ill. relates to this subject and discloses use of belts to accelerate threshed material.